Field of the Invention
The present invention relates to a system which informs a vehicle driver that another vehicle or pedestrian (moving obstacle) is approaching or moving away from a front detection area in response to detection of frequency deviation between the electric or ultrasonic waves transmitted by the system (Doppler radar) and the corresponding wave reflected from the moving obstacle, wherein detection of obstacles moving across the field of detection, rather than toward or away from the vehicle when the vehicle is stopped, is inhibited.